1. Field of the Invention
The invention relates to antenna arrangements for installation under dielectric covers, and more particularly to antennas for use in motor vehicle structures.
2. Description of the Related Art
It is common for motor vehicles such as cars, trucks, tractors, recreational vehicles and the like to use several antennas for such purposes as cellular telephones, CB, global positioning system (GPS), weatherband (WB), and the standard AM/FM radio. This proliferation of antennas is attended by special problems such as finding an appropriate mounting position for non-interfering operation as well as such inconveniences as high-speed antenna noise or “whistle.” Attempts have been made in the prior art to avoid external antennas and incorporate them into windowpanes and roof panels and the like.
Non-conducting materials such as fiberglass are now commonly used particularly in the construction of truck cabs in order to save weight. It is known to use flat plate antennas between the headliner and the nonconductive roof panel of truck cabs. See, for example, U.S. Pat. No. 5,402,134, U.S. Pat. No. 6,906,672, and the known use of three receiving wires of different lengths laid horizontally parallel or flared from a single attachment point where an AM receiving wire is typically 105 inches long, an FM wire 30 inches, and a WB wire 16 inches. Each of these known solutions has limitations in various applications, especially in the CB frequency range. Newer cabs are more aerodynamic with sweeping rooflines that have a more vertical component than prior rooflines.